Dimension Stone Group Australia (DSGA) own and operate high quality granite quarries at Fraser Range, near Norseman Western Australia. These quarries currently produce the Verde Austral, Garnet Ice and Fraser Range Black granites.


by JM Fetherston
Perth 2010

Verde Austral
Verde Austral is a very hard, gneissic granodiorite. It is coarse-grained, greenish-grey rock that assumes a deep olive-green colour when polished. It has a charnockitic tendency based on its mineral content of orthopyroxene, plagioclase and orthoclase feldspars, and bluish-tinged quartz. Minor minerals include hornblende, biotite, opaque oxide, apatite, and zircon.
The Verde Austral quarry is located at Mount Malcolm, 100 km east of Norseman and about 30 km southeast of the Eyre Highway (Fig. 9). Verde Austral was first recognized as a potential dimension stone by Maritana Gold NL in 1988. The company subsequently changed its name to Fraser Range Granite NL and began to develop the initial quarrying operation. In the mid-1990s, Norwegian quarrying methods including specialized dimension stone drilling, diamond wire block sawing, and the creation of 6 to 8 m high quarry faces, were introduced at the quarry to improve the quality and quantity of quarry blocks. Since that time, the operation has changed ownership to Allied Granites Pty Ltd, and finally to the current owners, Dimension Stone Group Australia Pty Ltd.
The Verde Austral deposit at Mount Malcolm consists of mining lease M63/235, that contains the operating quarry. A former contiguous mining lease, M63/276, also known as ‘The Dome’ immediately north of the quarry lease, contains additional stone resources of lesser quality.
At the quarry site, operations extend over a comparatively large area. Owing to the stone’s extreme hardness, and apparent paucity of jointing, the company has retained the 6 m-high quarry faces, but blocks are now cut entirely by diamond wire sawing to achieve maximum quality control. Operating quarry faces are orientated parallel to a steeply dipping, north-northeasterly trending foliation as it has been found that blocks cut parallel to this foliation plane produce the highest polish. Diamond wire sawing produces primary blocks 1.8 m wide x 6.0 m high x 8.0 m deep cut into the quarry wall (Fig. 10). In recent years, the area around the quarry has been drilled to 30 m depth. Results have shown that substantial resources of Verde Austral appear to be contained within a 200 m-wide, west-northwest trending zone. Currently, Dimension Stone Group Australia has opened a new bench at the lower 3rd level in the quarry exposing a high-quality, massive stone unbroken for depths of at least 8–10 m. The company estimates current dimension stone resources in the quarry area at about 6000 m3 (~ 16 000 t).
Verde Austral is a very hard rock making it extremely durable in exterior applications. It is amenable to precision cutting into greenish-grey blocks, slabs, tiles and other more complex shapes (Fig. 11). When polished it takes on a visually attractive deep olive-green hue (Appendix 4.4). It has excellent physical properties, particularly for strength, given by Melocco Stone (2009):
• Absorption 0.068%
• Bulk density 2.660 t/m3
• Compressive strength (dry) 240 MPa
• Modulus of rupture (dry) 12.7 MPa
• Flexural strength (dry) 16 MPa

Apart from some architectural and monumental applications for Verde Austral in Western Australia, the principal market appears to be in the eastern states, particularly in Sydney. In the mid-1990s the stone was used in the construction of prestigious buildings in Sydney City such as Governor Phillip Tower, Governor Macquarie Tower, First Government House Museum, and buildings at Darling Harbour, Later, the stone was one of three dimension stones specified by the Sydney City Council for use in upgrading public areas prior to the Olympic Games in 2000. For this purpose Verde Austral was used extensively as curb stones and paving slabs in main streets and public places in central Sydney. Other paving projects included the Channel 10 Building, Townhall House, and the Ritz Cinema, all in Sydney, and the Rockhampton Courthouse in Queensland.
More recently, applications for Verde Austral have begun to appear in Perth City with the redevelopment of the entrance to the Concert Hall (Fig. 12), the foyer of the Town Hall and a number of other sites in the city. It is understood that this stone may be used in the redevelopment of a number of public places in Perth in the near future.
Petrographic description
The gneissic granodiorite is weakly foliated and may be charnockitic. The visually estimated mineralogy includes 37% quartz, 42% plagioclase plus myrmekite, 10% orthoclase, 9–10% orthopyroxene, 1% hornblende and 0.5% opaque oxide plus biotite as well as apatite and trace zircon to 0.15 mm in diameter. Quartz is irregularly disseminated with amoeboid interlocking grains to 2.5 mm in diameter as well as lenses or bands with quartz to 15 mm long, parallel to the foliation and 7 mm wide. Plagioclase is mostly less than 3 mm in diameter, but the K-feldspar (orthoclase bead perthite) is as much as 8 mm in diameter and locally encloses plagioclase. Mafic lenses are elongate and define a slightly irregular anastomosing foliation. These lenses are mostly composed of pale-pink to green pleochroic orthopyroxene with less abundant olive-green hornblende and rare biotite as well as opaque oxide, apatite, and zircon. Fractures in orthopyroxene contain limonite and clay, with microfissures in feldspars also containing limonite.